How to configure window to fit content when resizing?

[pozix604]

The app code below displays a column of buttons, then an image to the right. The image has an aspect ratio of 2:1 and it resizes to the available width of the window.

I can resize the window to any size, which means that sometimes the image will be clipped at the bottom, and sometimes there will be empty space below the image.

How do I constrain the window resizing so that it always fits the content? It appears to be related to enabling/disable scrolling in the window but I cannot see how to achieve this. I can find no examples which illustrate how this is done. Pointers?

use eframe::egui::{
    self, load::SizedTexture, vec2, Button, Color32, ColorImage, Image, TextureHandle,
    TextureOptions,
};

struct App1 {
    th: TextureHandle,
}

impl App1 {
    fn new(cc: &eframe::CreationContext<'_>) -> Self {
        Self {
            th: cc.egui_ctx.load_texture(
                "texture",
                ColorImage::new([64, 32], Color32::RED),
                TextureOptions::NEAREST,
            ),
        }
    }
}

impl eframe::App for App1 {
    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
        egui::CentralPanel::default().show(ctx, |ui| {
            ui.horizontal_top(|ui| {
                let button_size = vec2(100.0, 50.0);
                ui.vertical(|ui| {
                    ui.add_sized(button_size, Button::new("one"));
                    ui.add_sized(button_size, Button::new("two"));
                    ui.add_sized(button_size, Button::new("three"));
                });
                let desired_size = ui.available_width() * vec2(1.0, 0.5);
                ui.allocate_ui(desired_size, |ui| {
                    ui.add(
                        Image::new(SizedTexture::new(&self.th, self.th.size_vec2()))
                            .shrink_to_fit(),
                    );
                });
            });
        });
    }
}

fn main() {
    eframe::run_native(
        "App",
        eframe::NativeOptions::default(),
        Box::new(|cc| Ok(Box::new(App1::new(cc)))),
    )
    .unwrap();
}